On Thursday, the first four of the elephants, due to be relocated over the next 10 days, were shot with tranquilliser darts from a helicopter near Narok, about 150 kilometres south of the capital, Nairobi, a notorious zone for human-wildlife conflict.

Let sleeping elephants lie ... a sedated elephant is loaded into a crate to be relocated to the Maasai Mara game reserve in an exercise involving 50 elephants. Photo: AFP

Once the giant animals lost consciousness, conservationists carefully winched them up by crane onto trucks for the journey to the Maasai Mara, from where they had been cut off by widening settlement, increasing farming and deforestation.

"The greatest challenge to Kenyan wildlife conservation today is Kenya's population growth," said the Kenya Wildlife Service director, Julius Kipng'etich.

Workers splashed the elephants with water to cool them before giving another injection to wake them up, ready for their 150-kilometre truck journey to the Maasai Mara.

If the operation is a success for the first 50 animals, wildlife service plans to move 200 of them.